1. Field of the Invention
The present invention relates to an image forming apparatus, and, more particularly, to a bypass tray of an image forming apparatus capable of preventing production of impactnoise or skewing of paper when the paper is fed through the bypass tray.
2. Description of the Related Art
In general, an image forming apparatus includes a paper loading unit to load a plurality of sheets of paper on which an image may then be formed. The paper loading unit generally includes a cassette having the plurality of sheets of paper, the cassette being detachably provided to a body of the image forming apparatus, and a bypass tray forming a part of a casing of the body to feed a sheet of a print medium, special paper, or the like.
FIGS. 1 and 2 are side views illustrating a process of picking up a sheet of paper from a conventional bypass tray.
Referring to FIGS. 1 and 2, the bypass tray includes a knock-up plate 10 with a plurality of sheets of paper S stacked thereon, a support 12 provided at one side of the knock-up plate 10, an idle roller 11 rotatably provided at one end of the support 12, and a resilient part 20 to resiliently bias the knock-up plate 10 upward, the resilient part 20 having one end fixed to the knock-up plate 10 and the other end fixed to a body (not shown) of the image forming apparatus.
The knock-up plate 10 is provided at an upper portion thereof with a pickup roller 32 fixed to a rotary shaft 30, which is rotatably provided to the body (not shown). The pickup roller 32 picks up the sheets of paper stacked on the knock-up plate 10 sheet by sheet. Idle rollers 31, idling around the rotary shaft 30, are provided to both sides of the pickup roller 32, respectively. The rotary shaft 30 is provided with a cam 33 having a latch portion 34 to secure the idle roller 11 provided to the support 12.
A process of picking up the paper from the conventional bypass tray will now be described with the accompanying drawings.
Referring to FIG. 1, since the latch portion 34 of the cam 33 latches the idle roller 11, the knock-up plate 10 is resiliently biased by the resilient part 20 upwardly, but is not moved upwardly.
When the rotary shaft 30 is rotated by a solenoid (not shown) which selectively transfers a power from a driving power (not shown) to the rotary shaft 30, the pickup roller 32 is rotated in a counterclockwise direction. Also, the cam 33 fixed to the rotary shaft 30 is rotated with the rotary shaft 30 in the counterclockwise direction.
At that time, the idle roller 11 is released from the latch portion 34, and is then rotated along an outer periphery 35 of the cam 33 in a clockwise direction. As such, the knock-up plate 10 is moved upward by a resilient force of the resilient part 20, so that the stacked paper S comes into contact with the rotating pickup roller 32, and the stacked paper is picked up sheet by sheet starting with an uppermost sheet.
A clockwise rotation of the rotary shaft 30 causes the latch portion 34 of the cam 33 to again latch the idle roller 11, as shown in FIG. 1. A next sheet is picked up by repeating the above process.
As the idle roller 11 moves along the outer periphery 35 of the cam 33, the knock-up plate 10 is moved up and down to impact the uppermost sheet of paper. Therefore, there is a problem in that impact noise is significantly produced whenever the paper is fed. In addition, an alignment of the paper S stacked on the knock-up plate 10 may be disrupted, which in turn may cause poor paper feeding, and thus skew.